Crystallization properties of acetylated β-(1–4)-d-xylan

The acetylation of xylan has a great influence on the physiology of plants and the properties of lignified tissues. However, the effect of acetylation on the crystallization of xylans is still unclear. In this study, homogeneous acetylation of deacetylated β-(1–4)-d-xylans to different degree of substitution (DS) was carried out. Two precipitation methods, i.e. ethanol and water, were used to precipitate acetylated xylans. With the assistance of perpropionylation and HMBC NMR spectra, the DS of acetylation was accurately determined. The crystallization properties of acetylated xylans at different DS were evaluated by X-ray diffraction. For ethanol precipitated acetylated xylans, it is amorphous at all DS except at DS = 2 showing diffraction peaks of xylan diacetate crystal. For water precipitated acetylated xylans, it shows diffraction peaks of xylan hydrate crystal between DS 0 and DS 0.6, while the appearance of xylan diacetate crystal peaks starts at DS 1.96. The forming of xylan diacetate crystal is very abrupt with the changes of DS.